Magnetoresistance effect element, magnetic head, magnetic reproducing apparatus, and magnetic memory

ABSTRACT

A magnetoresistance effect element comprises a magnetoresistance effect film including a magnetically pinned layer whose direction of magnetization is pinned substantially in one direction, a magnetically free layer whose direction of magnetization changes in response to an external magnetic field, and a nonmagnetic intermediate layer located between the pinned layer and the free layer; and a pair of electrodes electrically connected to said magnetoresistance effect film to supply a sense current perpendicularly to a film plane of said magnetoresistance effect film, The intermediate layer has a first layer including a first region whose resistance is relatively high and second regions whose resistance is relatively low. The sense current preferentially flows through the second regions when the current passes the first layer. Alternatively, the concentration of oxygen in the first layer may have a two-dimensional fluctuation, and a first region where the concentration of oxygen is equal to or higher than 40 atomic % and a second region where the concentration of oxygen is equal to or lower than 35 atomic % may be provided in the first layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2002-093358, filed on Mar. 28,2002; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a magnetoresistance effect element, a magnetichead, a magnetic reproducing apparatus, and a magnetic memory and moreparticularly, to a magnetoresistance effect element which has astructure where a sense current is passed perpendicularly to a filmplane of the magnetoresistance effect film, and to a magnetic head usingthe same, a magnetic reproducing apparatus and a magnetic memory.

In a certain kind of ferromagnetic substance, a phenomenon in whichresistance changes according to strength of an external magnetic fieldis known, and this is called the “magnetoresistance effect.” This effectcan be used for detection of an external magnetic field, and such amagnetic field detecting element is called “the magnetoresistance effectelement (it is also hereafter called “MR element”).”

Such a MR element is industrially used in a magnetic recording andreproducing apparatus, and used for read-out of information which isstored in a magnetic recording medium, such as a hard disk and magnetictape, (for example, IEEE MAG-7,150 (1971), and such a magnetic head iscalled a “MR head.”

In recent years, in a magnetic recording and reproducing device withwhich these MR elements are used, especially in a hard disk drive unit,the magnetic storage density is increased. As a result, the recordingbit size on the medium becomes smaller, and the quantity of leakingmagnetic flux from the recording bit, i.e., a signal lo magnetic field,is being smaller.

Therefore, it is becoming indispensable to realize a MR element whichhas a higher S/N ratio and higher sensitivity by obtaining a resistancerate of change at a lower magnetic field. This development serves asimportant base technology for improvement in storage density.

Here, “high sensitivity” means that an amount of resistance change (Ω)per unit magnetic field (Oe) is large. A MR element having a larger MRchanging rate and being excellent in the soft magnetic characteristicbecomes more sensitive. In order to realize a high S/N ratio, it isimportant to reduce a thermal noise as much as possible. For thisreason, it is not desirable that resistance of the element itselfbecomes large. For example, when using as a reading sensor for a harddisk drive, a resistance of about 5 ohms-30 ohms is desired as theelement resistance in order to realize a good S/N ratio.

From the background, it is becoming common to use the spin valve(spin-valve) film which can obtain big MR rate for a MR element used fora hard disk drive.

FIG. 12 is a conceptual diagram which illustrates the sectionalstructure of a spin valve film. That is, the spin valve film 100 has thestructure where a ferromagnetic layer F, a non-magnetic layer S, aferromagnetic layer P, and an antiferromagnetic layer A are laminated inthis order. Two ferromagnetic layers F and P which sandwich thenon-magnetic layer S therebetween are magnetically uncoupled.

Magnetization of one ferromagnetic layer P is fixed in one direction byan exchange bias which is applied from the antiferromagnetic layer A. Amagnetization of the ferromagnetic layer F is made rotatable easily byexternal magnetic fields (signal magnetic field etc.). By an externalmagnetic field, only magnetization of the ferromagnetic layer F can berotated, and thus, the relative angle of the magnetization direction oftwo ferromagnetic layers P and F can be changed. As a result, a largemagnetic resistance effect can be acquired (Phys. Rev. B, Vol. 45, 806(1992), J. Appl. Phys. Vol. 69, and 4774 (1991)).

Here, the ferromagnetic layer F is called a “free layer”, a “magneticfield reception layer”, or a “magnetization free layer” in many cases.The ferromagnetic layer P is called a “pinned layer” or a “magnetizationfixed layer.” The non-magnetic layer S is called a “spacer layer”, an“interface adjusting intermediate layer”, or a “intermediate layer.”

In the case of a spin valve film, magnetization of the free layer F,i.e., a ferromagnetic layer, rotates easily even in a lower field.Therefore, a raise in sensitivity is possible and it is suitable for MRelement for MR heads.

To such a spin valve element, in order to detect change of resistance bya magnetic field, it is necessary to pass a “sense current.”

Conventionally, a sense current is generally passed in parallel to thefilm plane, and resistance of a parallel to the film plane is measured.This method is generally called the “CIP (current-in-plane)” system.

In the case of a CIP system, it is possible to acquire about 10-20% ofvalue as a MR rate of change. In the magnetoresistance effect head ofthe shield type currently used, since a spin valve element is used inthe plane form almost near a square, resistance of MR element becomesalmost equal to the plane resistance value of MR film.

Thus, in the case of the spin valve film of a CIP system, it becomespossible by setting a field resistance value to 5 ohms-30 ohms toacquire the good S/N property.

Resistance of this level can be realized comparatively easily by makingthickness of the whole spin valve film thin. For this reason, atpresent, the spin valve film of a CIP system is generally used as a MRelement for MR heads.

However, in order to realize information reproduction with high storagedensity which exceeds 100 Gbits/inch², it is expected that the valuewhich exceeds 30% as a MR rate of change is needed. However, it isdifficult to acquire the value which exceeds 20% as a MR rate of changeby the conventional spin valve film. Therefore, it has been a bigtechnical subject for further improvement in the storage density howthis MR rate of change can be increased.

From such a viewpoint, the spin valve which inserted the “electronicreflective layer” into the pinned layer or the free layer in the CIP-SVfilm is proposed in order to increase MR rate of change. As theelectronic reflective layer, an oxide, a nitride, a fluoride, or aboride can be used.

For example, an electronic reflective layer can be inserted into thepinned layer and the free layer, respectively. By a spin valve film, ifelectronic scattering takes place at the interface of each layer, a meanfree path will decrease, and MR rate of change will decrease. On theother hand, by providing the electronic reflective layer ER to reflectelectrons, the mean free path of electrons is made to increase, and itbecomes possible to obtain large MR rate of change.

Moreover, in the case of this structure, the probability that anelectron will pass through the interface of a magnetic layer/nonmagneticlayer also goes up by reflecting electrons. For this reason, it becomespossible to acquire the same effect as the case in an artificial latticefilm, and MR rate of change increases.

However, also in this structure, since all electrons may not passthrough the interface of a magnetic layer/nonmagnetic layer, there is alimit in increase of MR rate of change. For this reason, it issubstantially difficult to realize large MR rate of change which exceeds20% and a practical amount of resistance change of 5 ohms-30 ohms in theCIP-SV film which has the electronic reflective layers

In contrast to this, a magnetoresistance effect element of a structureof passing sense current perpendicularly (current perpendicular toplane: CPP) to a film plane in the artificial lattice where magneticlayers and non-magnetic layers are laminated is proposed as a method ofobtaining large MR which exceeds 30%. (hereafter called a “CPP typeartficial-lattice”)

With a CPP type artificial lattice type magnetoresistance effectelement, electrodes are provided in the upper and lower sides of theartificial lattice where the ferromagnetic layers and the non-magneticlayers are laminated by turns, respectively, and sense current flowsperpendicularly to the film plane. With this structure, the probabilitythat sense current will cross a magnetic layer/non-magnetic layerinterface becomes high. Therefore, it becomes possible to acquire thegood interface effect, and big MR rate of change is obtained.

However, in such a CPP artificial lattice type film, it is necessary tomeasure a resistance perpendicular to the film plane of the artificiallattice SL which consists of a laminated structure of very thin metalfilms. This resistance will generally turn into a very small value.Therefore, with the CPP type artificial lattice, it has been animportant technical subject to enlarge resistance as much as possible.Conventionally, it was indispensable to make the connected area of theartificial lattice SL and Electrodes EL as small as possible, and toincrease the number of laminations of the artificial lattice SL, and toincrease the total thickness, in order to enlarge the resistance.

For example, when pattering of the form of an element is carried out at0.1 micrometer×0.1 micrometer, if Co layers (thickness:2 nm) and Culayers (thickness:2 nm) are laminated 10 times by turns, the totalthickness becomes 20 nm and the resistance of about 1 ohm may beobtained. However, the resistance is not large enough.

If it is considered from a viewpoint of resistance, it is indispensableto make it the artificial lattice type instead of a spin valve type, inorder to obtain sufficient head output and to use as a good readingsensor for hard disks in a CPP type structure.

On the other hand, to use MR element for a MR head, it is necessary tocontrol the magnetization of a magnetic layer and measure an externalmagnetic field efficiently. At the same time, it is required to formeach magnetic layer into a single magnetic domain so that a Barkhausennoise etc. may not occur. However, as mentioned above, it is needed tolaminate a magnetic layer and a non-magnetism layer repeatedly by turnsin order to earn resistance, and it is technically very difficult tocontrol magnetization by CPP type MR element individually to such manymagnetic layers.

Moreover, when using MR element for a MR head, it is necessary to makethe magnetization rotate very sensitively to a small signal magneticfield to that a large MR rate of change is obtained. For that, it isnecessary to increase the signal magnetic-flux density in a sensingportion, so that a larger amount of magnetization rotations are obtainedby the same magnetic-flux density. Therefore, it is necessary to makethe total Mst (magnetization×film thickness) of the layers wheremagnetization rotates by an external magnetic field small. However, witha CPP type MR element, in order to earn resistance, it is necessary tolaminate magnetic layers and non-magnetic layers repeatedly by turns.For this reason, Mst increases and it becomes difficult to raise thesensitivity to a signal magnetic flux.

Thus, in spite that MR rate of change in a case of a CPP artificiallattice type film exceeds 30%, the sensitivity needed as a MR sensor formagnetic heads is not obtained.

On the other hand, adopting a CPP system in the spin valve structureusing FeMn/NiFe/Cu/NiFe, FeMn/CoFe/Cu/CoFe, etc. is also considered.

That is, a sense current is perpendicularly passed to a film plane tothe laminated structure which has spin valve structure. However, in suchCPP type SV structure, in order to enlarge resistance, it is necessaryto thicken thickness of a magnetic layer to about 20 nm. Even in such acase, a resistance rate of change is only about 30% in 4.2K, and ispredicted that only about 15% of resistance rate of change of the halfmay be obtained in room temperature.

That is, by the spin valve film of a CPP system, only about 15% of MRrate of change is obtained. And Mst of a free layer must be enlarged.Therefore, sensitivity required as a MR sensor for heads may not beobtained.

As explained above, various structures, such as a spin valve of a CIPtype spin valve film, a CPP type artificial lattice, and a CPP type, areproposed. However, the present magnetic storage density is continuingthe rise of an annual rate of 60% or more, and the further outputincrease will be needed from now on. However, the spin valve film whichcan be used with high storage density which exceeds 100 Gbits/inch2 atpresent and which has suitable resistance and the large amount of MRchange, and serves as high sensitivity magnetically is difficult torealize.

SUMMARY OF THE INVENTION

According to an embodiment of the invention, there is provided amagnetoresistance effect element comprising: a magnetoresistance effectfilm including a magnetically pinned layer whose direction ofmagnetization is pinned substantially in one direction, a magneticallyfree layer whose direction of magnetization changes in response to anexternal magnetic field, and a nonmagnetic intermediate layer locatedbetween the pinned layer and the free layer, the nonmagneticintermediate layer having a first layer including a first region whoseresistance is relatively high and second regions whose resistance isrelatively low and configured to have the sense current preferentiallyflow through the second regions when an sense current passes the firstlayer; and a pair of electrodes electrically coupled to themagnetoresistance effect film and configured to supply the sense currentperpendicularly to a film plane of the magnetoresistance effect film.

According to other embodiment of the invention, there is provided amagnetoresistance effect element comprising: a magnetoresistance effectfilm including a magnetically pinned layer whose direction ofmagnetization is pinned substantially in one direction, a magneticallyfree layer whose direction of magnetization changes in response to anexternal magnetic field, and a nonmagnetic intermediate layer locatedbetween the pinned layer and the free layer, the nonmagneticintermediate layer having a first layer made: of an oxide, aconcentration of oxygen in the first layer having a two-dimensionalfluctuation, the first layer having a first region where theconcentration of oxygen is equal to or higher than 40 atomic % and asecond region where the concentration of oxygen is equal, to or lowerthan 35 atomic %; and a pair of electrodes electrically coupled to themagnetoresistance effect film and configured to supply a sense currentperpendicularly to a film plane of the magnetoresistance effect film.

According to other embodiment of the invention, there is provided amagnetic head comprising a magnetoresistance effect element having; amagnetoresistance effect film including a magnetically pinned layerwhose direction of magnetization is pinned substantially in onedirection, a magnetically free layer whose direction of magnetizationchanges in response to an external magnetic field, and a nonmagneticintermediate layer located between the pinned layer and the free layer;and a pair of electrodes electrically coupled to the magnetoresistanceeffect film to supply a sense current perpendicularly to a film plane ofthe magnetoresistance effect film, the nonmagnetic intermediate layerhaving a first layer including a first region whose resistance isrelatively high and second regions whose resistance is relatively low,and the sense current preferentially flowing through the second regionswhen the current passes the first layer.

According to other embodiment of the invention, there is provided amagnetic head comprising a magnetoresistance effect element having; amagnetoresistance effect film including a magnetically pinned layerwhose direction of magnetization is pinned substantial in one direction,a magnetically free layer whose direction of magnetization changes inresponse to an external magnetic field, and a nonmagnetic intermediatelayer located between the pinned layer and the free layer; and a pair ofelectrodes electrically coupled to the magnetoresistance effect film tosupply a sense current perpendicularly to a film plane of themagnetoresistance effect film, the nonmagnetic intermediate layer havinga first layer made of an oxide, a concentration of oxygen in the firstlayer having a two-dimensional fluctuation, and a first region where theconcentration of oxygen is equal to or higher than 40 atomic % and asecond region where the concentration of oxygen is equal to or lowerthan 35 atomic % being provided in the first layer.

According to other embodiment of the invention, there is provided amagnetic reproducing apparatus which reads information magneticallyrecorded in a magnetic recording medium, the magnetic reproducingapparatus comprising a magnetic head having a magnetoresistance effectelement including: a magnetoresistance effect film including amagnetically pinned layer whose direction of magnetization is pinnedsubstantially in one direction, a magnetically free layer whosedirection of magnetization changes in response to an external magneticfield, and a nonmagnetic intermediate layer located between the pinnedlayer and the free layer; and a pair of electrodes electrically coupledto the magnetoresistance effect film to supply a sense currentperpendicularly to a film plane of the magnetoresistance effect film,the nonmagnetic intermediate layer having a first layer including afirst region whose resistance is relatively high and second regionswhose resistance is relatively low, and the sense current preferentiallyflowing through the second regions when the current passes the firstlayer.

According to other embodiment of the invention, there is provided amagnetic reproducing apparatus which reads information magneticallyrecorded in a magnetic recording medium, the magnetic reproducingapparatus comprising a magnetic head having a magnetoresistance effectelement including: a magnetoresistance effect film including amagnetically pinned layer whose direction of magnetization is pinnedsubstantially in one direction, a magnetically free layer whosedirection of magnetization changes in response to an external magneticfield, and a nonmagnetic intermediate layer located between the pinnedlayer and the free layer; and a pair of electrodes electrically coupledto the magnetoresistance effect film to supply a sense currentperpendicularly to a film plane of the magnetoresistance effect film,the nonmagnetic intermediate layer having a first layer made of anoxide, a concentration of oxygen in the first layer having atwo-dimensional fluctuation, and a first region where the concentrationof oxygen is equal to or higher than 40 atomic % and a second regionwhere the concentration of oxygen is equal to or lower than 35 atomic %being provided in the first layer.

According to other embodiment of the invention, there is provided amagnetic memory comprising a plurality of magnetoresistance effectelements arranged in a matrix fashion, the magnetoresistance effectelement including: a magnetoresistance effect film including amagnetically pinned layer whose direction of magnetization is pinnedsubstantially in one direction, a magnetically free layer whosedirection of magnetization changes in response to an external magneticfield, and a nonmagnetic intermediate layer located between the pinnedlayer and the free layer; and a pair of electrodes electrically coupledto the magnetoresistance effect film to supply a sense currentperpendicularly to a film plane of the magnetoresistance effect film,the nonmagnetic intermediate layer having a first layer including afirst region whose resistance is relatively high and second regionswhose resistance is relatively low, and the sense current preferentiallyflowing through the second regions when the current passes the firstlayer.

According to other embodiment of the invention, there is provided amagnetic memory comprising a plurality of magnetoresistance effectelements arranged in a matrix fashion, the magnetoresistance effectelement including: a magnetoresistance effect film including amagnetically pinned layer whose direction of magnetization is pinnedsubstantially in one direction, a magnetically free layer whosedirection of magnetization changes in response to an external magneticfield, and a nonmagnetic intermediate layer located between the pinnedlayer and the free layer; and a pair of electrodes electrically coupledto the magnetoresistance effect film to supply a sense currentperpendicularly to a film plane of the magnetoresistance effect film,the nonmagnetic intermediate layer having a first layer made of anoxide, a concentration of oxygen in the first layer having atwo-dimensional fluctuation, and a first region where the concentrationof oxygen is equal to or higher than 40 atomic % and a second regionwhere the concentration of oxygen is equal to or lower than 35 atomic %being provided in the first layer.

As mentioned above, according to the embodiments of the invention, acurrent constriction effect can be obtained by providing an oxideintermediate layer which has a two-dimensional fluctuation of electricalconductivity, for example, and thereby a large change in resistance canbe attained in a CPP-type structure.

As a result, a magnetic field detection with a high sensitivity can bestably obtained and a magnetic head having a high output and high S/Neven at a high recording density and a magnetic reproducing apparatus,and a magnetic memory of the degree of high integration can be realizedwith low power consumption, and the merit on industry is great.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given herebelow and from the accompanying drawings of theembodiments of the invention. However, the drawings are not intended toimply limitation of the invention to a specific embodiment, but are forexplanation and understanding only.

In the drawings:

FIG. 1 is a conceptual diagram showing a cross-sectional structure ofthe magnetoresistance effect element according to the embodiment of theinvention;

FIG. 2 is a diagram which expresses notionally that the oxideintermediate layer 9 performs the current constriction;

FIG. 3 shows a structure having the magnetization free layer 6 below themagnetization pinned layer 4;

FIGS. 4 and 5 are conceptual diagrams which express typically theprincipal part structure of the magnetoresistance effect elementconcerning the embodiment of the invention;

FIG. 6 is a sectional view of the magnetic resistance effect element cutin the perpendicular direction to the medium opposite side P;

FIG. 7 is a perspective view of a magnetic head assembly at the distalend from an actuator arm 155 involved, which is viewed from the disk;

FIG. 8 is a conceptual diagram which exemplifies the matrix structure ofthe magnetic memory of the embodiment;

FIG. 9 is a conceptual diagram showing another example of the matrixstructure of the magnetic memory of the embodiment;

FIG. 10 is a conceptual diagram showing a principal part of the crosssectional structure of a magnetic memory according to an embodiment ofthe invention;

FIG. 11 shows the A-A′ line sectional view of the memory cell shown inFIG. 10; and

FIG. 12 is a conceptual diagram which illustrates the sectionalstructure of a spin valve film.

DETAILED DESCRIPTION

Hereafter, some embodiment of the invention will be explained, referringto the drawings.

FIG. 1 is a conceptual diagram showing a cross-sectional structure ofthe magnetoresistance effect element according to the embodiment of theinvention. That is, on the substrate electrode 1, a base layer 2, anantiferromagnetic film 3, a magnetization pinned layer 4, an interfaceadjusting intermediate layer 5A, an oxide intermediate layer 9, aninterface adjusting intermediate layer 5B, a magnetization free layer 6,a protection layer 7, and an upper electrode layer 8 are laminated inthe order.

This element is a CPP type magnetoresistance effect element where sensecurrent I (in the direction of the arrow in the figure or in a directionopposite to the arrow) is passed between the substrate electrode 1 andthe upper electrode layer 9.

It is possible to determine whether the element is TMR or GMR, byinvestigating its conduction properties, such as ohmic characteristics,temperature dependence of a resistance, etc.

The interface adjusting intermediate layers 5A and 5B and the oxideintermediate layer 9 have the role which intercepts the magneticcoupling between t a magnetization pinned layer 4 and the magnetizationfree layer 6. The interface adjusting intermediate layers 5A and 5B alsocontribute to the magnetic properties of the magnetic layers. Forexample, by providing the interface adjusting intermediate layer 5B, thefilm quality of the free layer 6 can be improved, since the layer 5Bacts as a buffer layer upon the film formation of the free layer 6.

Furthermore, the oxide intermediate layer 9 acts as a “currentconstriction layer.” That is, the oxide intermediate layer 9 has afunction of making the effective element size smaller and enlarging theamount of resistance change, by narrowing down the current path of sensecurrent I.

FIG. 2 is a diagram which expresses notionally that the oxideinter-mediate layer 9 performs the current constriction. As notionallyillustrated in FIG. 2, the oxide intermediate layer 9 has atwo-dimensional “fluctuation” of resistance in along its film plane.Therefore, the portions where the current concentrates exist and thecurrent constriction effect is acquired.

That is, the resistance of the oxide intermediate layer 9 is fluctuatingin a two-dimensional direction, and the high resistance regions 9A andlow resistance regions 9B exist. The sense current I supplied from theelectrode to the spin valve film is blocked by the high resistanceregions 9A in the oxide intermediate layer 9, and flows through the lowresistance regions 9B locally.

In the embodiment, since current flows through such low resistanceregions 9B, the electric characteristics related with the oxideintermediate layer 9 current is kept ohmic. On the other hand, in thecase of the so-called TMR (tunneling-magnetoresistance effect) element,an insulating layer is prepared between a pair of magnetic layers, andsense current passes this insulating layer by tunneling. Therefore, thecurrent characteristic over the insulating layer in a TMR element showsthe so-called “tunneling characteristic.”

On the other hand, in the case of the magnetoresistance effect elementof the embodiment, since the sense current passes through the lowresistance regions in the oxide intermediate layer 9, ohmiccharacteristics is attained. Therefore, when the element of thisembodiment is compared with TMR element, temperature characteristics ofcurrent etc. are different.

There is a method of investigating the relation between the sensecurrent and a magnetoresistance effect as one of methods to investigatewhether it is TMR-like or it is ohmic-like. In the case of TMR,stability is not acquired because a breakdown takes place easily, ifresistance is low. When there is a tendency for a magnetoresistance rateof change to decrease by increase of the sense current, a possibility ofbeing TMR is very high.

Alternatively, by investigating the temperature dependency ofresistance, it can be distinguished. That is, in a case of the ohmicelement, if temperature is lowered to about minus 200 degreescentigrade, a tendency for resistance to decrease compared with thestate of room temperature will be seen. On the other hand, in the caseof a TMR element, if temperature is lowered to about minus 200 degreescentigrade, a tendency for resistance to increase compared with thestate of room temperature will be seen.

Now, in order to realize such a two-dimensional “fluctuation” in themagnetoresistance effect element of the embodiment, it is not necessaryto form distinct low resistance regions 9B in the oxide intermediatelayer 9. Rather, the oxide intermediate layer 9 may be formed so that itmay be continuous. In other ward, the boundary of high resistance region9A and low resistance region 9B does not need to be clear. In the oxideintermediate layer 9, it is easier to realize a homogeneous distributionof the current path in the case where the concentration of the oxygencontinuously fluctuates in the two-dimensional direction, than in thecase where the clear metal parts are formed in the layer 9.

The concentration fluctuation of such an oxide can be investigated byperforming nano-EDX analysis. When oxygen concentration is too high,resistance becomes high and becomes less appropriate for an applicationto a magnetic head. For this reason, as for the oxygen concentration oflow resistance region 9B, it is desirable to keep it below 35 atomic %.If resistance is too low on the contrary, the effect of output increasewill not be acquired. For this reason, as for the oxygen concentrationof high resistance region 9A, it is desirable to keep it more than 40atomic %.

That is, if the portion of oxygen concentration below 35 atomic % andthe portion of oxygen concentration more than 40 atomic % are provided,it is compatible in resistance adjustment and magnetoresistance effectincrease. Moreover, it is easy to adjust to resistance with the onesuitable as a magnetic head where the portion of the oxygenconcentration more than 40 atomic % is larger than the portion of theconcentration below 35 atomic %

That is, it is a conceptual expression which was expressed in FIG. 2,and the high resistance region 9A and the low resistance region 9B donot need to be divided clearly. Rather, the region 9A and the region 9Bcan be formed so that the composition thereof is changing continuously.

In this specification, the term “homogeneous” means that no variation inthe relevant characteristic is found in the element of 0.1 micrometersquare. Since “fluctuation” of the conduction characteristic parallel inthe film plane will substantially disappear and the resistance betweenthe upper and lower electrodes of the element will become very high ifthe thickness of the oxide intermediate layer 9 becomes 3 nm or more, itbecomes unsuitable to a magnetoresistance effect element of magneticrecording equipment.

For this reason, as for the thickness of the oxide intermediate layer 9,it is desirable to set it 3 nm or less. Furthermore, it is moredesirable to set 2 nm or less. On the other hand, if the thickness ofthe oxide intermediate layer 9 is set to 0.4 nm or less, homogeneitywill be lost and the tendency for the insulation in the portion whichshould block current to fall and for the current constriction effect tofall will be seen. Therefore, as for the oxide intermediate layer's 9thickness, it is desirable that it is 0.4 nm or more.

As a method of giving the oxide intermediate layer 9 “fluctuation” whichproduces the current constriction effect, the method of forming theoxide intermediate layer 9 using a metal layer which cannot oxidizeeasily can be mentioned. When an oxidization process is performed to ametal layer containing the element chosen from copper (Cu), gold (Au),silver (Ag), platinum (Pt), palladium (Pd), iridium (Ir), osmium (Os),etc. by 1% to 50%, the oxide intermediate layer 9 having such“fluctuation” can be formed easily.

As the oxide intermediate layer's 9 mother metal, it is desirable tochoose at least one from the group consisting; boron (B), silicon (Si),germanium (germanium), tantalum (Ta), tungsten (WI, niobium (Nb),aluminum (aluminum), molybdenum (Mo), phosphorous (P), vanadium (V),arsenic (As), antimony (Sb), zirconium (Zr), titanium (Ti), zinc (Zn),lead (Pb), thorium (Th), beryllium (Be), cadmium (Cd), a scandium (Sc),lantern (La), yttrium (Y), praseodymium (Pr), chromium (Cr), tin (Sn),gallium (Ga), Indium (In), rhodium (Rh), palladium (Pd), magnesium (Mg),lithium (Li), barium (Ba), calcium (calcium), strontium (Sr), manganese(Mn), iron (Fe), cobalt (Co), nickel (nickel), rubidium (Rb), and rareearth metals.

Among the above-mentioned element group, it is especially desirable touse at least one of boron (B), silicon (Si), germanium (germanium),tungsten (W), niobium (Nb), molybdenum (Mo), phosphorous (P), vanadium(V), antimony (Sb), zirconium (Zr), titanium (Ti), zinc (Zn), a lead(Pb), chromium (Cr), tin (Sn), gallium (Ga), iron (Fe), cobalt (Co), andrare earth metals.

Although aluminum (Al) and tantalum (Ta) tend to form amorphous oxides,the above-mentioned element tends to form crystalline oxides. In thecase of the crystalline oxides, the deficit and excess of oxygen atomsaffect the conduction characteristic rather intensively, therefore, itbecomes easy to form the two-dimensional “fluctuations” of theconduction characteristic. By investigating the electron diffractionpattern of a nano-area, it is possible to determine whether it iscrystalline material.

It can be also judged from a lattice image taken by a TEM (transmissionelectron microscopy). That is, it must be crystalline material if aperiodic lattice image is seen.

Thus, as the material of the oxide intermediate layer 9, it is desirableto use oxides which include at least one of boron (B), silicon (Si),germanium (germanium), tungsten (W), niobium (Nb), molybdenum (Mo),phosphorous (PI, vanadium (V), antimony (Sb), zirconium (Zr), titanium(Ti), zinc (Zn), a lead (Pb), chromium (Cr), tin (Sn), gallium (Ga),iron (Fe), cobalt (Co), and rare earth metals by 1%-50%.

On the other hand, the interface adjusting intermediate layers 5A and 5Bare non-magnetic metal layers whose thicknesses are 1 nm or less. As thematerial of the interface adjusting intermediate layers 5A and 5B,copper (Cu), gold (Au), silver (Ag), platinum (Pt), palladium (Pd),iridium (Ir), osmium (Os), etc. can mainly be used.

As a material of the magnetization free layer 6, the metal magneticmaterial including at least one of nickel (nickel), iron (Fe), andcobalt (Co) as its main component may be used. In order to increase thesensitivity of a magnetic sensor and to decrease a Barkhausen noise, itis required to have the good soft magnetic characteristic. From thisviewpoint, as for the magnetization free layer 6, it is desirable tolaminate it in the direction of a crystal axis perpendicular to (111)which is the closest packed plane of a face-centered cubic lattice.However, a part of the layer 6 may be of a body-centered cubic lattice,of a hexagonal close-packed lattice, or of any other crystal structures.

If the thicknesses of the interface adjusting intermediate layers 5A and5B are set to 1 nm or more, the current which is once constricted in theoxide intermediate layer 9 will spread in these interface adjustingintermediate layers 5A and 5B. Therefore, before the current reaches themagnetic layer which contributes to the magnetoresistance effect, theconstriction effect will be lost. For this reason, as for thethicknesses of the interface adjusting intermediate layers 5A and 5B, itis desirable to set them 1 nm or less. Furthermore, it is more desirablethat they are 0.25 nm or less.

Supposing the interface adjusting intermediate-layer 5B is not provided,the magnetization free layer 6 will be directly formed on the oxideintermediate layer 9. In this case, a bad influence may be exerted uponthe film growth of the magnetization free layer 6, and the soft magneticcharacteristic of the layer 6 may be degraded. For this reason, it isbetter to prepare interface adjusting intermediate-layer 5B of a certainamount of thickness, which consists of material, such as the copper(Cu), gold (Au), silver (Ag), platinum (Pt), palladium (Pd), iridium(Ir), and osmium (Os), between the oxide intermediate layer 9 and themagnetization free layer 6. The interface adjusting intermediate-layer5B layer does not necessarily need to be a continuous film along itsfilm plane direction, and may be partially missing.

Moreover, in the state where the element was completed, interfaceadjusting intermediate-layer 5B does not need to constitute the shape ofa clear distinct layer. Interface adjusting intermediate-layer 5B may bediffused into the magnetization free layer 6 and/or the oxideintermediate layer 9 near the interfaces. If 10% or more of atoms whichform interface adjusting intermediate-layer 5B exist between the oxideintermediate layer 9 and the magnetization free layer 6, there willalmost be no degradation of the soft magnetic characteristic of themagnetization free layer 6, even if the interface adjustingintermediate-layer 5B is not formed as a clear distinct layer.

The existing ratio of these elements can be analyzed by the EDX (energydispersive x-ray spectroscopy) etc.

On the other hand, interface adjusting intermediate-layer 5A is notnecessarily required. However, if the interface adjustingintermediate-layer 5A is formed as a layer including an element such ascopper (Cu), gold (Au), silver (Ag), platinum (Pt), palladium (Pd),iridium (Ir), and osmium (Os), and if the thickness of theintermediate-layer 5A is adjusted suitably, degree of thetwo-dimensional “fluctuation” in conduction can be adjusted in the casewhere the oxide intermediate layer 9 includes elements such as, boron(B), silicon (Si), germanium (germanium), tungsten (W), niobium (Nb),molybdenum (Mo), phosphorous (P), vanadium (V), antimony (Sb), zirconium(Zr), titanium (Ti), zinc (Zn), a lead (Pb), chromium (Cr), tin (Sn),galium (Ga), iron (Fe), cobalt (Co), and rare earth metals by 1%-50%.

Such an adjusting function of interface adjusting intermediate-layer 5Acan also be simultaneously given to another interface adjustingintermediate-layer 5B.

That is, metal, such as copper (Cu), gold (Au), silver (Ag), platinum(Pt), palladium (Pd), iridium (Ir), and osmium (Os), is advantageousmetal in order to give two-dimensional “fluctuation” of the degree ofconduction to the oxide intermediate layer 9. It becomes easy to formthe two-dimensional “fluctuation” of the degree of conduction, byforming interface adjusting intermediate-layers 5A or 5B with such metaland by supplying such metal element to the oxide intermediate layer 9from the interface adjusting intermediate-layers 5A or 5B by diffusionetc.

On the other hand, a sputtering using the target which consists of analloy of the substance used for the above-mentioned interface adjustmentintermediate layer and the substance used for the oxide layer isadvantageous to form the two-dimensional “fluctuation” of the degree ofconduction. The sintered target may also be used which includes elementsthat do not form a solid solution.

Moreover, as illustrated in FIG. 3, in the structure having themagnetization free layer 6 below the magnetization pinned layer 4(substrate side), the effect that is the same with having describedabove can be acquired. However, the influence which interface adjustmentintermediate-layer 5B has on the soft magnetic characteristic of themagnetization free layer 6 is far small compared with the structureshown in FIG. 1.

Therefore, degradation of the soft magnetic characteristic of themagnetization free layer 6 is hardly occurred, even if the concentrationof the atom which forms the interface adjusting intermediate-layer 5B isbelow 10% at the interface between the oxide intermediate layer 9 andthe magnetization free layer 6.

Moreover, in a case of the so-called “dual spin valve structure” wherethe magnetization pinned layers are provided in the upper and lowersides of the magnetization free layer, the above-mentioned situationholds similarly.

In the invention, as the magnetization pinned layer 4, the so-called“synthetic anti-ferromagnetic structure“ where two or more magneticlayers are coupled in an anti-ferromagnetic fashion by a non-magneticlayer such as a ruthenium (Ru) layer can also be used.

As explained above, according to the embodiment, the constriction of thesense current can be realized, effectual element size can be made to beable to reduce, and a large resistance change can be obtained, byproviding the oxide intermediate layer 9 which has unique structure.

As the result, the CPP type magnetoresistance effect element of highsensitivity can be offered.

Hereafter, the example of such a magnetoresistance effect element andthe example adapting the magnetoresistance effect element are explained.

FIRST EXAMPLE

First, the first example of the invention will be explained.

In this example, the magnetoresistance effect element of the structureexpressed in FIG. 1 was manufactured with the comparative example.

That is, after forming the substrate electrode 1, the spin valve of thefollowing film structure was formed on it:

-   -   5Ta/2Ru/15PtMn/4        CoFe/1Ru/4CoFe/intermediate-layer/4CoFe/1Cu/10Ta

In the above, each number expresses the thickness (in nanometer) of thelayer. This structure was formed by a DC magnetron sputtering. Then,annealing of 10 hours was performed at 270 degrees centigrade. And apatterning process was carried out to the planer shape into squareswhose sizes ranged from 0.15 microns to 3 microns. Furthermore, afterthe surroundings of the patterned spin valve were filled up withinsulators, such as alumina and a silicon oxide, the upper electrode 8was formed, and thus the element having a structure of passing currentperpendicularly to a film plane was completed.

Table 1 shows the structures of the intermediate layers in eachmanufactured element and the characteristic thereof. Resistance and theamount of resistance change (mΩμm²) were normalized to the element sizeof 1 micron square, respectively.

Measurement of an electrical property was performed at about 0.1 mA to20 mA using a constant current source. The multiplication of theresistance change and the sense current is obtained as an output.

As oxidization processing, oxyecoia partial pressure was made into therange of about 10⁻³ Pa to 10⁻² Pa, and exposure for about 200 secondswas performed by using a vacuum chamber whose background pressure was3×10⁻⁶ Pa.

The sintered target of Cr—Cu was used to form the oxide layer.

Here, sample (1) is the comparative sample of the metal base whereoxidation processing was not carried out.

Samples (2), (3), (4), and (5) are samples which have the interfaceadjusting intermediate layers of different thicknesses, respectively. Itis seen that if the oxide layer is formed, resistance increases and theamount of resistance change also increases. When the interface adjustingintermediate layer is thickened, resistance and the amount of resistancechange decrease quickly. And if an interface adjusting intermediatelayers thickness exceeds 1 nm, the amount of resistance change becomesequivalent to or even lower than the sample of a metal base, a meritwill completely be lost. If an interface adjusting intermediate layer isnot prepared, the soft magnetic characteristic of the magnetization freelayer is lost and it becomes difficult to obtain a stable film qualityand to obtain elements having a constant characteristic.

Samples (6), (7), (8), and (9) have the oxide layers of differentthicknesses, respectively. The amount of resistance change increases asresistance becomes larger. In a case where resistance exceeds 1000mΩμm2, the element resistance becomes too large and problems, such asgeneration of heat, occur when the element is processed into the headcorresponding to the track width of 0.1 to 0.2 micrometers, For thisreason, as for resistance of an element, it is desirable that it is lessthan 1000 mΩμm².

Samples (10), (11), and (12) are for investigating the dependability ofthe characteristic by the difference in the concentration of an oxidizedCu—Cr layer. If the concentration of Cr is high, the amount ofresistance change can be increased efficiently. If the concentration ofCr becomes 50% or less, most effects of output increase will not beacquired.

Among samples (1)-(12), sample (2) has the film characteristic which ismost suitable for head formation in respect of the resistance as well asthe amount of resistance change.

Moreover, as a result of investigating about the thickness dependabilityof the samples which had Cu₁₀Al₉₀ layers to be oxidized, it turned outthat the same effect is acquired. However, since there is a tendency forthe optimal thickness of the layer to be oxidized to become thinner,thickness control becomes more difficult. At the same time, thevariation in the characteristic for every element may arise.

On the other hand, there are some methods which enables a more stableformation of a thin oxide film. For example, oxidation can be performedby activating the surface of a sample using rare gas ions. Or before theoxidizing step, the surface of a sample can be improved by irradiatingwith ions. Or, before the oxidizing step, the surface of a sample can beimproved by an annealing treatment. If these methods are used, a thinoxide film can be formed with sufficient reproducibility.

Table 2 shows the result oxidized by using these methods. Here, in thecase of samples (14)-(18), the surface of aluminium90Cu10 was oxidizedby a natural oxidation treatment. On the other hand, in the case ofsamples 19-21, oxidization of the samples was performed, afterirradiating with ions. From Table 2 shows, it is clear that thecomparatively higher magnetoresistance effect is obtained in the sampleshaving performed the ion irradiation. Moreover, the variation of data islarger in the case of the samples formed by a natural oxidation.

When samples (19) and (20) are compared with samples (22) and (23), itturns out that the slightly high magnetoresistance effect is obtainedfor samples (19) and (20). That is, if thickness of an upper interfaceadjusting layer is thickened from 0.2 nm to 0.5 nm, a magnetoresistanceeffect will fall slightly. However, this fall is in a negligible range.

Moreover, when samples (1)-(13) are compared with samples (14)-(23), therange of the thickness where the optimal characteristic is acquired isdifferent. That is, it turned out that the optimum thickness rangediffers for Cr90Cu10 and AlCu.

Moreover, in the sample (1)-(23), coercivity of a free layer was 15 orless Oe. In contrast, it turned out by another experiment that when anupper interface adjusting intermediate layer was not provided in thesesamples, coercivity of the free layer became in the range of 50-100 Oe.

If coercivity of the free layer becomes such a high level, thesensitivity of the magnetoresistance effect element degraded. Thus, itturned out that by providing the upper interface adjusting layer, thecoercivity of the free layer can be decreased.

It is considered that the upper interface adjusting intermediate layeracts as a buffer on the formation of the free layer. That is, byproviding the upper interface adjusting layer, the film quality of thefree layer can be improved. Thus, magnetic property of the free layer isimproved.

Furthermore, as a result of investigating also about the materials ofthe interface adjusting intermediate layer the oxide intermediate layer,a certain amount of effect was acquired in all the material systemsenumerated in the above, respectively. Moreover, the effect was seenalso by using Ag, Pd, Os, Ir, and Pt as the material of the interfaceadjusting intermediate layer. Moreover, also in any of the substanceenumerated in the above as the material of the oxide intermediate layer,it was confirmed that the effect was acquired.

When the sections of samples (2) and (3) were observed by TEM, thecontinuous oxides without a “break” were formed along the paralleldirection to the film plane. In these sections, when EDX analysis wasperformed for every nanometer along the parallel direction to the filmplane of the oxide intermediate layers, a distribution of 5 to 50% wereseen for oxygen concentration. That is, a two-dimensional fluctuation ofthe concentration was seen. When the same observation was performed tosample (6), the oxide layer was discontinuous and oxygen concentrationwas in a range of 0 to 5%. This corresponds with resistance being toolow and there being no effect over an output.

Moreover, when sense current was changed and measurement was performedto the range of 50 mV output voltage about sample (6), the resistancerate of change became the same value substantially in all sense current.It is a greatly different point from TMR element, since TMR elementshows several % of phenomenon in a resistance rate of change in the sameexperiment.

In the invention, the upper and lower interface adjusting intermediatelayers does not need to have the same thickness. That is, as for thethickness of the upper interface adjusting intermediate layer, about 0.1nm is desirable in order to improve the soft magnetic characteristic ofthe magnetization free layer. On the other hand, even if the lowerinterface adjusting intermediate layer is not formed, the rise of themagnetoresistance effect is acquired. However, in respect of resistanceadjustment, it is advantageous to provide the lower interface adjustingintermediate layer which makes the resistance adjustment easier.Moreover, the effect of the same improvement in a magnetoresistanceeffect was acquired also with the structures where upside down reversalof these structures were carried out.

As explained above in full detail, referring to examples, it turned outthat the optimal resistance and the optimal magnetoresistance effect fora magnetic head can be obtained by adjusting the thicknesses of theinterface adjusting intermediate layer and oxide intermediate layer.

SECOND EXAMPLE

Next, the example of the CPP type magnetoresistance effect element whichcan be used as a magnetic head is given and explained as the secondexample of the invention.

FIGS. 4 and 5 are conceptual diagrams which express typically theprincipal part structure of the magnetoresistance effect elementconcerning the embodiment of the invention. That is, these figuresexpress the state there the magnetoresistance effect element is includedin the magnetic head. FIG. 4 is a sectional view of themagnetoresistance effect element cut in parallel to the medium facingsurface P which is opposite to a magnetic recording medium (not shown).FIG. 5 is a sectional view of the magnetic resistance effect element cutin the perpendicular direction to the medium opposite side P.

The magnetoresistance effect element illustrated in FIGS. 4 and 5 has ahard abutted structure. The lower electrode 12 and the upper electrode20 are provided in the upper and lower sides of the magnetoresistanceeffect film 14, respectively. Moreover, as expressed in FIG. 5, the biasmagnetic field applying film 16 and the insulating film 18 are laminatedand provided in the both sides of the magnetoresistance effect film 14.Furthermore, as illustrated in FIG. 5, the protection layer 30 isprovided in the medium facing surface of the magnetoresistance effectfilm 14.

The magnetoresistance effect film 14 has the structure according to theembodiment of the invention mentioned above referring to FIGS. 1 and 2.That is, the oxide intermediate layer who has the two-dimensional“fluctuation” of the degree of electric conduction is provided, and alarge resistance change can be obtained by CPP type current supply.

The sense current to the magnetoresistance effect film 14 is passed in aperpendicular direction to the film plane, as indicated by the arrow A,with the electrodes 12 and 20 arranged at the upper and lower sides.Moreover, a bias magnetic field is applied to the magnetoresistanceeffect film 14 with a pair of bias magnetic field applying films 16 and16 provided in right and left.

By this bias magnetic field, magnetic anisotropy of the free layer ofthe magnetoresistance effect film 14 can be controlled and formed into asingle magnetic domain. As a result, magnetic domain structure can bestabilized, and the Barkhausen noise due to the movement of magneticwall can be suppressed.

According to the invention, MR rate of change improves by providing theoxide intermediate layer which has two-dimensional “fluctuation” of thedegree of electric conduction in the magnetoresistance effect film 14.As a result, it becomes possible to improve the sensitivity of amagnetoresistance effect element notably. And for example, when it isapplied to a magnetic head, magnetic reproduction of high sensitivity isattained.

THIRD EXAMPLE

Next, a magnetic reproducing apparatus having inboard themagnetoresistance effect element of the embodiment will be explained asthe third example of the invention.

That is, the magnetoresistance effect element or the magnetic headexplained with reference to FIGS. 1 through 5 can be incorporated in arecording/reproducing magnetic head assembly and mounted in a magneticreproducing apparatus.

FIG. 6 is a perspective view that shows outline configuration of thiskind of magnetic reproducing apparatus. The magnetic reproducingapparatus 150 shown here is of a type using a rotary actuator. Amagnetic reproducing medium disk 200 is mounted on a spindle 152 androtated in the arrow A direction by a motor, not shown, which isresponsive to a control signal from a controller of a driving mechanism,not shown. The magnetic reproducing apparatus 150 shown here may have aplurality of medium disks 200 inboard.

The medium disk 200 may be of a “lateral recording type” in whichdirections of the recording bits are substantially in parallel to thedisk surface or may be of a “perpendicular recording type” in whichdirections of the recording bits are substantially perpendicular to thedisk surface.

A head slider 153 for carrying out recording and reproduction ofinformation to be stored in the medium disk 200 is attached to the tipof a film-shaped suspension 154. The head slider 153 supports amagnetoresistance effect element or magnetic head, for example,according to one of the foregoing embodiments of the invention, near thedistal end thereof.

Once the medium disk 200 rotates, the medium-facing surface (ABS) of thehead slider 153 is held floating by a predetermined distance above thesurface of the medium disk 200. Also acceptable is a so-called“contact-traveling type” in which the slider contacts the medium disk200.

The suspension 154 is connected to one end of an actuator arm 155 havinga bobbin portion for holding a drive coil, not shown, and others. At theopposite end of the actuator arm 155, a voice coil motor 156, a kind oflinear motor, is provided. The voice coil motor 156 comprises a drivecoil, not shown, wound on the bobbin portion of the actuator arm 155,and a magnetic circuit made up of a permanent magnet and an opposed yokethat are opposed to sandwich the drive coil.

The actuator arm 155 is supported by ball bearings, not shown, which arelocated at upper and lower two positions of the spindle 157 and drivenby the voice coil motor 156 for rotating, sliding movements.

FIG. 7 is a perspective view of a magnetic head assembly at the distalend from an actuator am 155 involved, which is viewed from the disk. Themagnetic head assembly 160 includes the actuator arm 155 having thebobbin portion supporting the drive coil, for example, and thesuspension 154 is connected to one end of the actuator arm 155.

At the distal end of the suspension 154, a head slider 153 carrying themagnetoresistance effect element as explained with reference to FIGS. 1through 5 is provided. The suspension 154 has a lead 164 for writing andreading signals, and the lead line 164 is connected to electrodes of themagnetic head incorporated in the head slider 153. Numeral 165 in FIG. 7denotes an electrode pad of the magnetic head assembly 160.

According to this example, one of the magnetoresistance effect elementsalready explained in conjunction with the aforementioned embodiments isused as the magnetoresistance effect element, information magneticallyrecorded on the medium disk 200 under a higher recording density thanbefore can be read reliably.

FOURTH EXAMPLE

Next, a magnetic memory having the magnetoresistance effect element ofthe embodiment will be explained as the fourth example of the invention.That is, a magnetic memory such as a magnetic random access memory(MRAM), where memory cells are arranged in the shape of a matrix can berealized by using the magnetoresistance effect element of theembodiment.

FIG. 8 is a conceptual diagram which exemplifies the matrix structure ofthe magnetic memory of the embodiment. That is, this figure shows thecircuit structure of the embodiment in the case of having arranged thememory cells each of which includes a magnetoresistance effect elementmentioned above with reference to FIGS. 1 through 5, in the shape of amatrix array.

In order to choose one bit in an array, it has the sequence decoder 350and the line decoder 351. By selecting the bit, line 334 and the wordline 332, specific switching transistor 330, is turned on and a specificcell is chosen uniquely. And the bit information recorded on themagnetic-recording layer which constitutes the magnetoresistance effectelement 321 can be read by detecting with a sense amplifier 352.

When writing in bit information, writing current is passed in thespecific write-in word line 323 and the specific bit line 322,respectively, and the current magnetic field is applied to the recordinglayer of a specific cell.

FIG. 9 is a conceptual diagram showing another example of the matrixstructure of the magnetic memory of the embodiment. That is, in the caseof this example, the bit lines 322 and word lines 334 which were wiredin the shape of a matrix are chosen by decoders 360 and 361,respectively, and the specific memory cell in an array is chosenuniquely.

Each memory cell has the structure where Diode D is connected with themagnetoresistance effect element 321 in series. Here, Diode D has therole to prevent that sense current detours in memory cells other thanmagnetoresistance effect element 321 selected.

In writing, write-in current is passed in a specific bit line 322 and aword line 323, thereby applying the current magnetic field to therecording layer of a specific cell.

FIG. 10 is a conceptual diagram showing a principal part of the crosssectional structure of a magnetic memory according to an embodiment ofthe invention.

And FIG. 11 shows the A-A line sectional view.

That is, the structure shown in these figures corresponds to the memorycell of the 1-bit portion of the magnetic memory which operates as arandom access memory.

This memory cell consists of a storage cell portion 311 and a transistorportion 312 for address selection. The storage cell portion 311 has themagnetoresistance effect element 321 and a pair of wiring 322 and 324connected to the element 321. The magnetoresistance effect element 321has a structure mentioned with reference to FIGS. 1 through 5, and showsa large magnetoresistance effect.

What is necessary is to pass sense current for the magnetoresistanceeffect element 321 in the case of bit information read-out, and just todetect the resistance change. In addition, the magnetization free layerof the magnetoresistance effect element can be used as the magneticrecording layer.

A selecting transistor 330 connected through a via 326 and buried wiring328 is formed in a transistor portion 312 for selection. This transistor330 carries OUT switching operation according to the voltage applied toa gate 332, and controls switching of the current path between themagnetoresistance effect element 321 and wiring 334.

Moreover, under the magnetoresistance effect element, the write-inwiring 323 is formed in the direction which intersects the wiring 322.These write-in wirings 322 and 323 can be formed with the alloycontaining aluminum (aluminum), copper (Cu), tungsten (W), tantalum(Ta), or one of these.

In a memory cell of such structure, when writing bit information in themagnetoresistance effect element 321, a write-in pulse current is passedto the wirings 322 and 323. Then, a synthetic magnetic field induced bythese current is applied to a record layer, and magnetization of arecord layer of the magnetoresistance effect element can be reversedsuitably.

On the other hand, when reading bit information, sense current is passedthrough wiring 322, the magnetoresistance element 321 containing amagnetic-recording layer, and the lower electrode 324, and a change ofthe resistance of the magnetoresistance effect element 321 or resistanceitself is measured.

By using the magnetoresistance effect element mentioned with referenceto FIGS. 1 through 5, a large magnetoresistance effect is obtained.Therefore, a stable read-out can be performed even if the cell size isreduced to realize a large capacity storage.

Heretofore, embodiments of the invention have been explained in detailwith reference to some specific examples. The invention, however, is notlimited to these specific examples.

For example, material, shape and thickness of the ferromagnetic layer,anti-ferromagnetic layer, insulating film and ferromagnetic film of themagnetoresistance effect element according to the invention may beappropriately selected by those skilled in the art within the knowntechniques to carry out the invention as taught in the specification andobtain equivalent effects.

Further, in a case where the magnetoresistance effect element of theinvention is applied to a magnetic head, by providing magnetic shieldson upper and lower side of the element, the reproducing resolution canbe regulated.

It will be also appreciated that the invention is applicable not only tooptically-assisted magnetic heads or magnetic recording apparatuses ofthe lengthwise recording type but also to those of the perpendicularmagnetic recording type and ensures substantially the same effects.

Further, the magnetic reproducing apparatus according to the presentinvention may be of a fixed type in which specific magnetic recordingmedium is permanently installed, while it may be of a removable type inwhich the magnetic recording medium can be replaced easily.

Further, also concerning the magnetic memory according to the invention,those skilled in the art will be able to carry out the invention byappropriately selecting a material or a structure within the knowntechniques.

While the present invention has been disclosed in terms of theembodiment in order to facilitate better understanding thereof. Itshould be appreciated that the invention can be embodied in various wayswithout departing from the principle of the invention. Therefore, theinvention should be understood to include all possible embodiments andmodification to the shown embodiments which can be embodied withoutdeparting from the principle of the invention as set forth in theappended claims. TABLE 1 RESISTANCE RESISTANCE CHANGE SAMPLE LAYERSEQUENCE (mΩ · μm²) (mΩ · μm²) MR RATE (%) SAMPLE 1 5Cu 80 0.6 0.8SAMPLE 2 0.1Cu/0.6Cu₁₀Cr₉₀/OXIDATION TREATMENT/0.1Cu 500 20 4.0 SAMPLE 30.2Cu/0.6Cu₁₀Cr₉₀/OXIDATION TREATMENT/0.2Cu 380 10 2.6 SAMPLE 40.5Cu/0.6Cu₁₀Cr₉₀/OXIDATION TREATMENT/0.5Cu 200 2 1.0 SAMPLE 52Cu/0.6Cu₁₀Cr₉₀/OXIDATION TREATMENT/2Cu 130 0.4 0.3 SAMPLE 60.1Cu/0.4Cu₁₀Cr₉₀/OXIDATION TREATMENT/0.1Cu 90 0.7 0.8 SAMPLE 70.1Cu/0.5Cu₁₀Cr₉₀/OXIDATION TREATMENT/0.1Cu 400 11 2.8 SAMPLE 80.1Cu/0.7Cu₁₀Cr₉₀/OXIDATION TREATMENT/0.1Cu 1000 28 2.8 SAMPLE 90.1Cu/0.8Cu₁₀Cr₉₀/OXIDATION TREATMENT/0.1Cu 2500 31 1.2 SAMPLE 100.1Cu/0.6Cr/OXIDATION TREATMENT/0.1Cu 800 19 2.4 SAMPLE 110.1Cu/0.6Cu₂₀Cr₈₀/OXIDATION TREATMENT/0.1Cu 450 15 3.3 SAMPLE 120.1Cu/0.6Cu₃₀Cr₇₀/OXIDATION TREATMENT/0.1Cu 290 5 1.7 SAMPLE 130.1Cu/0.6Cu₆₀Cr₄₀/OXIDATION TREATMENT/0.1Cu 100 0.6 0.6

TABLE 2 RESISTANCE RESISTANCE CHANGE SAMPLE LAYER SEQUENCE (mΩ · μm²)(mΩ · μm²) MR RATE (%) SAMPLE 14 0.2Cu/0.6AlCu/NATURAL OXIDATION/0.2Cu250 1.75 0.7 SAMPLE 15 0.2Cu/0.7AlCu/NATURAL OXIDATION/0.2Cu 410 3.690.9 SAMPLE 16 0.2Cu/0.8AlCu/NATURAL OXIDATION/0.2Cu 1000 14 1.4 SAMPLE17 0.2Cu/0.9AlCu/NATURAL OXIDATION/0.2Cu 3200 25.6 0.8 SAMPLE 180.2Cu/0.6AlCu/RARE GAS ION + NATURAL OXIDATION/0.2Cu 200 34 1.7 SAMPLE19 0.2Cu/0.7AlCu/RARE GAS ION + NATURAL OXIDATION/0.2Cu 300 6 2 SAMPLE20 0.2Cu/0.8AlCu/RARE GAS ION + NATURAL OXIDATION/0.2Cu 450 22.5 5SAMPLE 21 0.2Cu/0.9AlCu/RARE GAS ION + NATURAL OXIDATION/0.2Cu 580 23.24 SAMPLE 22 0.2Cu/0.7AlCu/RARE GAS ION + NATURAL OXIDATION/0.5Cu 295 5.61.8 SAMPLE 23 0.2Cu/0.8AlCu/RARE GAS ION + NATURAL OXIDATION/0.5Cu 43020.21 47

1. A magnetoresistance effect element comprising: a magnetoresistanceeffect film including a magnetically pinned layer whose direction ofmagnetization is pinned substantially in one direction, a magneticallyfree layer whose direction of magnetization changes in response to anexternal magnetic field, and a nonmagnetic intermediate layer locatedbetween the pinned layer and the free layer, the nonmagneticintermediate layer having a first layer including a first region whoseresistance is relatively high and second regions whose resistance isrelatively low and configured to have the sense current preferentiallyflow through the second regions when an sense current passes the firstlayer; and a pair of electrodes electrically coupled to themagnetoresistance effect film and configured to supply the sense currentperpendicularly to a film plane of the magnetoresistance effect film. 2.The magnetoresistance effect element according to claim 1, wherein thefirst region and the second regions are formed in correspondence with atwo-dimensional fluctuation of concentration of oxygen in the firstlayer.
 3. The magnetoresistance effect element according to claim 1,wherein a composition of the nonmagnetic intermediate layer changescontinuously at a boundary between the first and second regions.
 4. Themagnetoresistance effect element according to claim 1, wherein an ohmiccharacteristic is obtained when the sense current passes the firstlayer.
 5. The magnetoresistance effect element according to claim 1,wherein the first layer includes a oxide of a element selected from thegroup consisting of boron (B), silicon (Si), germanium (germanium),tantalum (Ta), tungsten (W), niobium (Nb), aluminum (aluminum),molybdenum (Mo), phosphorous (P), vanadium (V), arsenic (As), antimony(Sb), zirconium (Zr), titanium (Ti), zinc (Zn), lead (Pb), thorium (Th),beryllium (Be), cadmium (Cd), a scandium (Sc), lantern (La), yttrium(Y), praseodymium (Pr), chromium (Cr), tin (Sn), galium (Ga), Indium(In), rhodium (Rh), palladium (Pd), magnesium (Mg), lithium (Li), barium(Ba), calcium (calcium), strontium (Sr), manganese (Mn), iron (Fe),cobalt (Co), nickel (nickel), rubidium (Rb), and rare earth metals, asits main component.
 6. The magnetoresistance effect element according toclaim 1, wherein the first layer includes an element selected from thegroup consisting of copper (Cu), gold (Au), silver (Ag), platinum (Pt),palladium (Pd), iridium (Ir), and osmium (Os), in a range from 1 atomic% to 50 atomic %.
 7. The magnetoresistance effect element according toclaim 1, wherein the first layer is substantially crystalline.
 8. Themagnetoresistance effect element according to claim 1, wherein the firstlayer includes a oxide of a element selected from the group consistingof boron (B), silicon (Si), germanium (Ge), tungsten (W), niobium (Nb),molybdenum (Mo), phosphorous (P), vanadium (V), antimony (Sb), zirconium(Zr), titanium (Ti), zinc (Zn), a lead (Pb), chromium (Cr), tin (Sn),gallium (Ga), iron (Fe), cobalt (Co), and rare earth metals, and furtherincludes an element selected from the group consisting of copper (Cu),gold (Au), silver (Ag), platinum (Pt), palladium (Pd), idium (Ir), andosmium (Os), in a range from 1 atomic % to 50 atomic %.
 9. Themagnetoresistance effect element according to claim 1, wherein thenonmagnetic intermediate layer further has a second layer made of anon-magnetic metal.
 10. The magnetoresistance effect element accordingto claim 9, wherein a thickness of the second layer is equal to orsmaller than 1 nanometer.
 11. The magnetoresistance effect elementaccording to claim 9, wherein the non-magnetic metal is a one selectedfrom the group consisting of copper (Cu), gold (Au), silver (Ag),platinum (Pt), palladium (Pd), iridium (Ir), and osmium (Os).
 12. Amagnetoresistance effect element comprising: a magnetoresistance effectfilm including a magnetically pinned layer whose direction ofmagnetization is pinned substantially in one direction, a magneticallyfree layer whose direction of magnetization changes in response to anexternal magnetic field, and a nonmagnetic intermediate layer locatedbetween the pinned layer and the free layer, the nonmagneticintermediate layer having a first layer made of an oxide, aconcentration of oxygen in the first layer having a two-dimensionalfluctuation, the first layer having a first region where theconcentration of oxygen is equal to or higher than 40 atomic % and asecond region where the concentration of oxygen is equal to or lowerthan 35 atomic %; and a pair of electrodes electrically coupled to themagnetoresistance effect film and configured to supply a sense currentperpendicularly to a film plane of the magnetoresistance effect film.13. The magnetoresistance effect element according to claim 12, whereina composition of the nonmagnetic intermediate layer changes continuouslyat a boundary between the first and second regions.
 14. Themagnetoresistance effect element according to claim 12, wherein an ohmiccharacteristic is obtained when the sense current passes the firstlayer.
 15. The magnetoresistance effect element according to claim 12,wherein the oxide includes a element selected from the group consistingof boron (B), silicon (Si), germanium (germanium), tantalum (Ta),tungsten (W), niobium (Nb), aluminum (aluminum), molybdenum (Mo),phosphorous (P), vanadium (V), arsenic (As), antimony (Sb), zirconium(Zr), titanium (Ti), zinc (Zn), lead (Pb), thorium (Th), beryllium (Be),cadmium (Cd), a scandium (Sc), lantern (La), yttrium (Y), praseodymium(Pr), chromium (Cr), tin (Sn), gallium (Ga), Indium (In), rhodium (Ph),palladium (Pd), magnesium (Mg), lithium (Li), barium (Ba), calcium(calcium), strontium (Sr), manganese (Mn), iron (Fe), cobalt (Co),nickel (nickel), rubidium (Rb), and rare earth metals, as its maincomponent.
 16. The magnetoresistance effect element according to claim12, wherein the first layer includes an element selected from the groupconsisting of copper (Cu), gold (Au), silver (Ag), platinum (Pt),palladium (Pd), iridium (Ir), and osmium (Os), in a range from 1 atomic% to 50 atomic %.
 17. The magnetoresistance effect element according toclaim 12, wherein the first layer is substantially crystalline.
 18. Themagnetoresistance effect element according to claim 12, wherein theoxide includes a element selected from the group consisting of boron(B), silicon (Si), germanium (Ge), tungsten (W), niobium (Nb),molybdenum (Mo), phosphorous (P), vanadium (V), antimony (Sb), zirconium(Zr), titanium (Ti), zinc (Zn), a lead (Pb), chromium (Cr), tin (Sn),gallium (Ga), iron (Fe), cobalt (Co), and rare earth metals, and furtherincludes an element selected from the group consisting of copper (Cu),gold (Au), silver (Ag), platinum (Pt), palladium (Pd), iridium (Ir), andosmium (Os), in a range from 1 atomic % to 50 atomic %.
 19. Themagnetoresistance effect element according to claim 12, wherein thenonmagnetic intermediate layer further has a second layer made of anon-magnetic metal.
 20. The magnetoresistance effect element accordingto claim 19, wherein a thickness of the second layer is equal to orsmaller than 1 nanometer.
 21. The magnetoresistance effect elementaccording to claim 19, wherein the non-magnetic metal is a one selectedfrom the group consisting of copper (Cu), gold (Au), silver (Ag),platinum (Pt), palladium (Pd), irdium (Ir), and osmium (Os).
 22. Themagnetoresistance effect element according to claim 9, wherein thesecond layer is provided between the first layer and the magneticallypinned layer, or between the first layer and the magnetically freelayer.
 23. The magnetoresistance effect element according to claim 19,wherein the second layer is provided between the first layer and themagnetically pinned layer, or between the first layer and themagnetically free layer.
 24. A magnetic head comprising amagnetoresistance effect element having; a magnetoresistance effect filmincluding a magnetically pinned layer whose direction of magnetizationis pinned substantially in one direction, a magnetically free layerwhose direction of magnetization changes in response to an externalmagnetic field, and a nonmagnetic intermediate layer located between thepinned layer and the free layer, and a pair of electrodes electricallycoupled to the magnetoresistance effect film to supply a sense currentperpendicularly to a film plane of the magnetoresistance effect film,the nonmagnetic intermediate layer having a first layer including afirst region whose resistance is relatively high and second regionswhose resistance is relatively low, and the sense current preferentiallyflowing through the second regions when the current passes the firstlayer.
 25. A magnetic head comprising a magnetoresistance effect elementhaving; a magnetoresistance effect film including a magnetically pinnedlayer whose direction of magnetization is pinned substantially in onedirection, a magnetically free layer whose direction of magnetizationchanges in response to an external magnetic field, and a nonmagneticintermediate layer located between the pinned layer and the free layer;and a pair of electrodes electrically coupled to the magnetoresistanceeffect film to supply a sense current perpendicularly to a film plane ofthe magnetoresistance effect film, the nonmagnetic intermediate layerhaving a first layer made of an oxide, a concentration of oxygen in thefirst layer having a two-dimensional fluctuation, and a first regionwhere the concentration of oxygen is equal to or higher than 40 atomic %and a second region where the concentration of oxygen is equal to orlower than 35 atomic % being provided in the first layer.
 26. A magneticreproducing apparatus which reads information magnetically recorded in amagnetic recording medium, the magnetic reproducing apparatus comprisinga magnetic head having a magnetoresistance effect element including; amagnetoresistance effect film including a magnetically pinned layerwhose direction of magnetization is pinned substantially in onedirection, a magnetically free layer whose direction of magnetizationchanges in response to an external magnetic field, and a nonmagneticintermediate layer located between the pinned layer and the free layer;and a pair of electrodes electrically coupled to the magnetoresistanceeffect film to supply a sense current perpendicularly to a film plane ofthe magnetoresistance effect film, the nonmagnetic intermediate layerhaving a first layer including a first region whose resistance isrelatively high and second regions whose resistance is relatively low,and the sense current preferentially flowing through the second regionswhen the current passes the first layer.
 27. A magnetic reproducingapparatus which reads information magnetically recorded in a magneticrecording medium, the magnetic reproducing apparatus comprising amagnetic head having a magnetoresistance effect element including: amagnetoresistance effect film including a magnetically pinned layerwhose direction of magnetization is pinned substantially in onedirection, a magnetically free layer whose direction of magnetizationchanges in response to an external magnetic field, and a nonmagneticintermediate layer located between the pinned layer and the free layer;and a pair of electrodes electrically coupled to the magnetoresistanceeffect film to supply a sense current perpendicularly to a film plane ofthe magnetoresistance effect film, the nonmagnetic intermediate layerhaving a first layer made of an oxide, a concentration of oxygen in thefirst layer having a two-dimensional fluctuation, and a first regionwhere the concentration of oxygen is equal to or higher than 40 atomic %and a second region where the concentration of oxygen is equal to orlower than 35 atomic % being provided in the first layer.
 28. A magneticmemory comprising a plurality of magnetoresistance effect elementsarranged in a matrix fashion, the magnetoresistance effect elementincluding: a magnetoresistance effect film including a magneticallypinned layer whose direction of magnetization is pinned substantially inone direction, a magnetically free layer whose direction ofmagnetization changes in response to an external magnetic field, and anonmagnetic intermediate layer located between the pinned layer and thefree layer; and a pair of electrodes electrically coupled to themagnetoresistance effect film to supply a sense current perpendicularlyto a film plane of the magnetoresistance effect film, the nonmagneticintermediate layer having a first layer including a first region whoseresistance is relatively high and second regions whose resistance isrelatively low, and the sense current preferentially flowing through thesecond regions when the current passes the first layer.
 29. A magneticmemory comprising a plurality of magnetoresistance effect elementsarranged in a matrix fashion, the magnetoresistance effect elementincluding: a magnetoresistance effect film including a magneticallypinned layer whose direction of magnetization is pinned substantially inone direction, a magnetically free layer whose direction ofmagnetization changes in response to an external magnetic field, and anonmagnetic intermediate layer located between the pinned layer and thefree layer; and a pair of electrodes electrically coupled to themagnetoresistance effect film to supply a sense current perpendicularlyto a film plane of the magnetoresistance effect film, the nonmagneticintermediate layer having a first layer made of an oxide, aconcentration of oxygen in the first layer having a two-dimensionalfluctuation, and a first region where the concentration of oxygen isequal to or higher than 40 atomic % and a second region where theconcentration of oxygen is equal to or lower than 35 atomic % beingprovided in the first layer.